Considerable attention has been paid to the research of passive and active structural control for wind-induced self-excited vibration of long-span bridges in recent years. In this paper a passive aerodynamic control of bridge flutter is proposed. The system consists of two additional surfaces to generate stabilizing forces. The torsional motion of the surfaces is governed by the additional pendulum attached to the bridge deck. The state-space equation of the flutter control system is derived through the rational function approximation of the unsteady aerodynamics of the bridge section. The performance of the control system is evaluated for various parameters of the pendulum and the potential improvement of flutter wind speed is demonstrated through numerical examples. The experimental study showed very good agreement with the theoretical prediction for small amplitude motion of the control surfaces.